Abrasive articles and methods of making and using the same

ABSTRACT

A coated abrasive article having a reinforced vulcanized fiber backing with an abrasive layer affixed thereto and methods of making and using the same. The reinforced vulcanized fiber backing contains a reinforcing material that comprises a reaction product of a curable material.

BACKGROUND

Vulcanized fiber has been in commerce since the 19^(th) century. Theterm “vulcanized fiber”, sometimes also referred to as “vulcanizedfibre” or “fish paper”, refers to a leather-like material generallyformed from cellulose by compressing layers of chemically treated (e.g.,as with metallic chlorides) cellulose derived from paper, paper pulp,rayon or cloth. Due to its hydrophilic nature, vulcanized fiber istypically prone to absorb moisture.

Coated abrasive articles typically have an abrasive layer affixed to abacking. Vulcanized fiber has been used as a backing material for coatedabrasive articles for more than 60 years. One well-recognized problem ofusing vulcanized fiber backings in abrasive articles is shape distortion(e.g., curling or cupping) of the coated abrasive article due to changesin environmental moisture content (e.g., humidity). Shape distortion mayoccur, for example, during manufacturing, during storage, or during use.Further, the shape distortion may occur toward and/or away from theabrasive layer. An example of such distortion of a prior art coatedabrasive article having a vulcanized fiber backing is shown in FIG. 1,wherein the coated abrasive article exhibits curling directed away fromthe abrasive layer. If excessive shape distortion occurs duringmanufacturing of the coated abrasive article, then it is typicallydiscarded as scrap material. Further, if excessive shape distortionoccurs during storage, or in use, it typically results in productcomplaints, reduced product sales, and/or reduced product performance.

Attempts to solve the problem of shape distortion date back more than 50years. For example, U.S. Pat. No. 2,431,258 to H. P. Kirchner, filedFeb. 5, 1946, issued Nov. 18, 1947 states in col. 2, lines 23-30:“Although it is possible by this process to make discs which areinitially of the desired curvature, a great deal of trouble isexperienced by abrasive manufacturers by reason of the fact thatvulcanized fiber is very susceptible to changes in atmospheric moisturecontent, particularly when one side of the material has been coated asis the case with the abrasive discs of this invention.” In that patent,the problem was addressed by drying the article to achieve the desiredlevel of curvature and then covering the vulcanized fiber backing with asheet of material that is impermeable to moisture vapor. From that timeuntil the present, there have been developed various other alternativemoisture insensitive and dimensionally stable backings for coatedabrasive articles incorporating vulcanized fiber.

Notwithstanding these various products, and primarily for economicreasons, vulcanized fiber backings are still used today in thecommercial manufacture of coated abrasive articles primarily. Forexample, the major coated abrasives manufacturers each market coatedabrasive products with vulcanized fiber backings that are prone tohumidity problems, even though alternative moisture insensitive anddimensionally stable backings for coated abrasive articles are known.Accordingly, there remains a need in the coated abrasives industry forcoated abrasive products with vulcanized fiber backings that areeconomical to manufacture and that are not prone to unacceptable levelsof shape distortion with changes in humidity levels.

SUMMARY

In one aspect, the present invention provides a coated abrasive articlecomprising a reinforced vulcanized fiber backing having first and secondmajor surfaces, the first major surface having an abrasive layer affixedthereto, wherein the reinforced vulcanized fiber backing has areinforcing material distributed substantially throughout the vulcanizedfiber backing, wherein the reinforcing material comprises from 0.1 to 20percent by weight, based on the combined weight of the reinforcingmaterial and vulcanized fiber backing, and wherein the reinforcingmaterial comprises a reaction product of an aqueous organic curablematerial selected from the group consisting of phenolic resins,aldehydes, aminoplasts, urea-formaldehyde resins, polyaziridines,polyepoxides, polyisocyanates, curable latex emulsions, and combinationsthereof.

In another aspect, the present invention provides a method of abrading asurface of a workpiece, the method comprising: providing a coatedabrasive article according to the present invention, frictionallycontacting the abrasive layer with a surface of the workpiece, andmoving at least one of the abrasive layer and the surface of theworkpiece relative to the other to abrade at least a portion of thesurface of the workpiece.

In yet another aspect, the present invention provides a method of makinga coated abrasive article, the method comprising:

impregnating a vulcanized fiber backing having first and second majorsurfaces with a curable material;

at least partially curing the curable material to provide a reinforcingmaterial wherein the reinforcing material comprises from 0.1 to 20percent by weight, based on the combined weight of the reinforcingmaterial and vulcanized fiber backing, and wherein the reinforcingmaterial comprises a reaction product of an aqueous organic curablematerial selected from the group consisting of phenolic resins,aldehydes, aminoplasts, urea-formaldehyde resins, polyaziridines,polyepoxides, polyisocyanates, curable latex emulsions, and combinationsthereof; and

affixing an abrasive layer to the first major surface of the reinforcedvulcanized fiber backing.

Coated abrasive articles according to the present invention typicallyexhibit a low degree of shape distortion with changes in humidity.Surprisingly, it is also found that such articles exhibit improved cutas compared to prior coated abrasives without reinforcing material inthe vulcanized fiber backing.

As used herein,

the term “aqueous” means dissolved and/or dispersed in a liquid vehiclecomprising water; and

the term “organic” means containing carbon.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a photograph of a coated abrasive disc of the prior art;

FIG. 2 is a cross-sectional side view of an exemplary coated abrasivearticle according to the present invention;

FIG. 3 is a cross-sectional side view of an exemplary coated abrasivearticle according to the present invention; and

FIG. 4 is a photograph of a coated abrasive disc coated abrasive articleaccording to Example 10.

DETAILED DESCRIPTION

In general, coated abrasive articles have abrasive particles affixed toa backing. More typically, coated abrasive articles comprise a backinghaving two major opposed surfaces and an abrasive layer affixed to onemajor surface of the backing. The abrasive layer typically comprisesabrasive particles and a binder, wherein the binder serves to secure theabrasive particles to the backing.

In one embodiment, the coated abrasive article has an abrasive layercomprising a make layer, a size layer, and abrasive particles. In makingsuch a coated abrasive article, a make layer comprising a first binderprecursor is applied to one major surface of the backing, and optionallypartially cured. Abrasive particles are then at least partially embeddedinto the make layer (e.g., via electrostatic coating), and the firstbinder precursor is sufficiently cured (i.e., crosslinked) to secure theparticles to the make layer. A size layer comprising a second binderprecursor is then applied over the make layer and abrasive particles,followed by curing of the binder precursors. Such coated abrasivearticles may further comprise an optional supersize disposed on at leasta portion of the abrasive layer. If present, the supersize layertypically includes grinding aids and/or anti-loading materials.

In another embodiment, the coated abrasive article has an abrasive layeraffixed to one major surface of a backing, wherein the abrasive layer isprovided by applying a slurry comprised of binder precursor and abrasiveparticles onto a major surface of a backing, and then curing the binderprecursor.

The backing comprises vulcanized fiber, a dense material of partiallyregenerated cellulose in which the fiber structure is retained and whichis typically calendered to provide a relatively smooth surface.Vulcanized fiber is widely available from commercial sources such as,for example, Franklin Fibre—Lamitex Corporation (Wilmington, Del.) orYangmin Ind. Trade Co., Ltd. (Sanmenxia, Henan, China).

Typically, vulcanized fiber backing useful for preparing coated abrasivearticles according to the present invention has a thickness in a rangeof from 0.02 to 5 millimeters, for example, from 0.05 to 2.5 millimetersor from 0.1 to 1 millimeter, although thinner and thicker vulcanizedpaper backings may also be used. Further, the density of the vulcanizedfiber is typically in a range of from 0.9 to 1.5 grams per cubiccentimeter, although higher and lower density vulcanized fiber may alsobe used.

The vulcanized fiber backing is impregnated (i.e., thoroughly permeated)with a curable material, typically comprising at least one curableresin, which then is at least partially cured, for example, by dryingand heating to provide a reinforced vulcanized fiber backing.Impregnation of the vulcanized fiber with the curable material may beachieved by any suitable saturation coating method including, forexample, roll coating, dip coating, or spraying. The curable material istypically impregnated into the vulcanized fiber such that it isdistributed throughout the body of the vulcanized fiber, for example, ina substantially uniform manner. Typically, the variation inconcentration of the curable material on going from one major surface ofthe backing to the other should not typically exceed about a factor oftwo, however any concentration gradient may be used as long as theresultant reinforcing material is distributed throughout the vulcanizedfiber backing. Although substantially uniform distribution of both thecurable material and the reinforcing material is typically preferred, itwill be recognized that a minor amount of local variations orinterruptions in the distribution (e.g., coating voids) may be toleratedwithout significant adverse effects.

At least one of the vulcanized fiber sheet and the reinforced vulcanizedfiber backing may optionally further comprise additional backingtreatments such as a backsize (i.e., a layer affixed to the majorsurface of the backing opposite the major surface having the abrasivelayer), a presize (i.e., a layer affixed to the backing on the majorsurface having the abrasive layer), a tie layer (i.e., a layer betweenthe abrasive layer and the major surface to which the abrasive layer isaffixed), and/or a subsize treatment. A subsize is similar to a saturant(i.e., a backing treatment applied by a process that includes saturatingthe backing with the saturant) except that it is applied to a previouslytreated backing. An antistatic material may be included in any of thesebacking treatments. The addition of an antistatic material can reducethe tendency of the coated abrasive article to accumulate staticelectricity when sanding wood or wood-like materials. Additional detailsregarding antistatic backings and backing treatments can be found in,for example, U.S. Pat. No. 5,108,463 (Buchanan); U.S. Pat. No. 5,137,542(Buchanan et al.); U.S. Pat. No. 5,328,716 (Buchanan); and U.S. Pat. No.5,560,753 (Schnabel et al.); the disclosures of which are incorporatedherein by reference.

Typically, the reinforcing material comprises from 0.1 to 20 percent byweight, based on the combined weight of the reinforcing material andvulcanized fiber backing. For example, the reinforcing material maycomprise from 1 to 15 percent, or even from 5 to 15 percent, by weight,based on the combined weight of the reinforcing material and vulcanizedfiber backing.

Typically, the reinforced vulcanized fiber backing will have a thicknessin a range of from 0.15 to 1.8 millimeters, for example, 0.5 to 1.3millimeters, or even 0.8 to 0.9 millimeters, although thicker andthinner reinforced vulcanized fiber backings may also be used.

The reinforcing material is distributed substantially throughout (i.e.,through at least 80 percent by volume of) the reinforced vulcanizedfiber backing. For example, the reinforcing material may besubstantially uniformly distributed within the vulcanized fiber backing.The reinforcing material comprises at least one material that is areaction product of at least one aqueous organic curable materialselected from the group consisting of phenolic resins, aldehydes,aminoplasts, urea-formaldehyde resins, polyaziridines, polyepoxides,polyisocyanates, curable latex emulsions, and combinations thereof. Insome embodiments, the aqueous organic curable material may contain watermiscible organic co-solvents. In addition, the reinforcing material mayinclude one or more optional additives such as, for example, fillers,plasticizers, antistatic agents, antioxidants, or colorants.

As used herein, the term “phenolic resin” refers to a syntheticthermosetting resin obtained by the reaction of a phenol with analdehyde. For example, a portion of the phenol can be substituted withone or more other phenols such as resorcinol, m-cresol, 3,5-xylenol,t-butylphenol and p-phenylphenol. Likewise, a portion of theformaldehyde can be substituted with other aldehyde groups such asacetaldehyde, chloral, butyraldehyde, furfural or acrolein.

Examples of phenolic resins include resole-phenolic resins and novolakphenolic resins. Resole phenolic resins have a molar ratio offormaldehyde to phenol of greater than or equal to one to one, typicallybetween 1.5:1.0 and 3.0: 1.0. Novolak phenolic resins have a molar ratioof formaldehyde to phenol of less than one to one.

Typical resole phenolic resins contain a base catalyst. The presence ofa basic catalyst speeds up the reaction or polymerization rate of thephenolic resin. The pH of resole phenolic resins is typically from 6 to12, more typically from 7 to 10, and even more typically from 7 to 9.Examples of suitable basic catalysts include sodium hydroxide, potassiumhydroxide, calcium hydroxide, magnesium hydroxide, barium hydroxide, andcombinations thereof. Typical catalysts for the reaction of formaldehydewith phenol are chosen from group I and II metal salts, generallybecause of their high reactivity and low cost. Amines are also used tocatalyze the phenylaldehyde reaction. The amount of basic catalyst istypically 5 percent by weight or less, more typically 2 percent byweight or less, and even more typically 1 percent by weight or lessbased on the weight of the phenolic resin. Resole phenolic resins areusually made from phenol and formaldehyde.

Phenolic resins are typically coated as a solution with water and/ororganic solvent (e.g., alcohol). Typically, the solution includes about70 percent to about 85 percent solids by weight, although otherconcentrations may be used. If the solids content is very low, then moreenergy is required to remove the water and/or solvent. If the solidscontent is very high, then the viscosity of the resulting phenolic resinis too high which typically leads to processing problems.

Examples of useful aldehydes include monoaldehydes such as formaldehydeand acetaldehyde and dialdehydes such as glyoxal, malonaldehyde,succinaldehyde, and glutaraldehyde.

Examples of useful aminoplasts include those available under the tradedesignations “CYMEL 373” and “CYMEL 323” from Cytec Inc., Stamford,Conn.

Examples of useful urea-formaldehyde resins include that marketed underthe trade designation “AL3029R” from Borden Chemical (Columbus, Ohio),and those marketed under the trade designations “AMRES LOPR”, “AMRESPR247HV” and “AMRES PR335CU” from Georgia Pacific Corp. (Atlanta, Ga.).

Examples of useful polyaziridines include trimethylolpropanetris-(N-aziridinyl)propionate) andpentaerythritol-tris-(-(N-aziridinyl)propionate), available from BayerCorporation (Pittsburgh, Pa.) under the trade designations “XAMA-220”and “XAMA-7”, respectively; (tris[1-(2-ethyl)aziridinyl]phosphine oxide,available from Aceto Chemical Corporation (Lake Success, N.Y.) under thetrade designation “MAPO”; and a polyaziridine available from Neoresins,Inc. (Wilmington, Mass.) under the trade designation “CROSSLINKERCX-100”.

Examples of useful polyisocyanates include monomeric, oligomeric, andpolymeric polyisocyanates (e.g., diisocyanates and triisocyanates), andmixtures and blocked versions thereof. Polyisocyanates may be aliphatic,aromatic, and/or a mixture thereof.

Examples of useful polyepoxides include monomeric polyepoxides,oligomeric polyepoxides, polymeric polyepoxides, and mixtures thereof.The polyepoxides may be aliphatic, aromatic, or a mixture thereof.

Examples of alicyclic polyepoxides monomers includeepoxycyclohexane-carboxylates (e.g., 3,4-epoxycyclohexylmethyl3,4-epoxycyclohexanecarboxylate (e.g., as available under the tradedesignation “ERL-4221” from Dow Chemical Co. (Midland, Mich.);3,4-epoxy-2-methylcyclohexylmethyl3,4-epoxy-2-methylcyclohexane-carboxylate,bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6-methylcyclohexylmethyl3,4-epoxy-6-methylcyclohexanecarboxylate (e.g., as available under thetrade designation “ERL-4201” from Dow Chemical Co.); vinylcyclohexenedioxide (e.g., as available under the trade designation “ERL-4206” fromDow Chemical Co.); bis(2,3-epoxycyclopentyl)ether (e.g., as availableunder the trade designation “ERL-0400” from Dow Chemical Co.),bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate (e.g., as available underthe trade designation “ERL-4289” from Dow Chemical Co.), dipentericdioxide (available, for example, under the trade designation “ERL-4269”from Dow Chemical Co.),2-(3,4-epoxycyclohexyl-5,1′-spiro-3′,4′-epoxycyclohexane-1,3-dioxane,and 2,2-bis(3,4-epoxycyclohexyl)propane, and polyepoxide resins derivedfrom epichlorohydrin.

Examples of aromatic polyepoxides include polyglycidyl ethers ofpolyhydric phenols such as: Bisphenol A-type resins and theirderivatives, including such epoxy resins having the trade designation“EPON” available from Resolution Performance Products, Houston, Tex.;epoxy cresol-novolac resins; Bisphenol-F resins and their derivatives;epoxy phenol-novolac resins; and glycidyl esters of aromatic carboxylicacids (e.g., phthalic acid diglycidyl ester, isophthalic acid diglycidylester, trimellitic acid triglycidyl ester, and pyromellitic acidtetraglycidyl ester), and mixtures thereof. Commercially availablearomatic polyepoxides include, for example, those having the tradedesignation “ARALDITE” available from Ciba Specialty Chemicals,Tarrytown, N.Y.; aromatic polyepoxides having the trade designation“EPON” available from Resolution Performance Products; and aromaticpolyepoxides having the trade designations “DER”, “DEN”, and “QUATREX”available from Dow Chemical Co.

Polyepoxide(s) are typically combined with a curing agent such as forexample, a polyamine, polyamide, polythiol, or an acidic catalyst,although may not be required for curing.

Examples of useful curable latex emulsions include those curable latexemulsions derived from styrene, butadiene, acrylonitrile, chloroprene,polyesters, polyurethanes, polyvinyl acetate, acrylate and/ormethacrylate esters, acrylamides, acrylic and/or methacrylic acid, andcopolymers thereof. Mixtures of curable latex emulsions may also beused.

Commercially available curable latex emulsions include, for example,those available under the trade designations “RHOPLEX” and “ACRYSOL”from Rohm and Haas Company (Philadelphia, Pa.); “FLEXCRYL” and “VALTAC”from Air Products & Chemicals Inc. (Allentown, Pa.); “SYNTHEMUL”,“TYCRYL”, and “TYLAC” from Dow Reichold Specialty Latex, LLC (ResearchTriangle Park, N.C.), “HYCAR”, “CARBOCURE”, “GOOD-RITE”, “SANCURE” and“VYCAR” from NOVEON (Cleveland, Ohio); “CHEMIGUM” commercially availablefrom Goodyear Tire and Rubber Co. (Akron, Ohio), “NEOCRYL” commerciallyavailable from ICI; and “BUTAFON” commercially available from BASF.Unless the latex is self-curing (i.e., self-crosslinking), it istypically used in combination with at least one additive (e.g., acrosslinker) that facilitates curing or it may also be used incombination with another curable material.

Examples of commercially available self-curing latexes include thoseemulsions having the trade designations “CARBOCURE TSR-72” and“CARBOCURE TSR-201”; styrene butadiene emulsions having the tradedesignation “GOOD-RITE SB-1168”, “GOOD-RITE SB-0706”, “GOOD-RITE1800×73”; a polyurethane dispersion having the trade designation“SANCURE AU-4010” (acrylic urethane hybrid); a polyvinyl acetateemulsion having the trade designation “VYCAR VA-0450”; and a poly(vinylchloride)-acrylic copolymer having the trade designation “VYCAR TN-810”;all marketed by Noveon, Cleveland, Ohio.

The curable material may optionally contain one or more curatives, forexample, as described above, or in addition thereto. The choice ofcurative is typically determined by the curable material selected andmay include, for example, acid, base, photocatalyst, hardeners,crosslinkers, and mixtures thereof.

As noted above, coated abrasive articles typically have an abrasivelayer affixed to a backing. Typically, the abrasive layer comprises makeand size layers and abrasive particles or, alternatively, a layer ofabrasive particles dispersed in a binder.

According to one embodiment of the present invention, the coatedabrasive article has an abrasive layer comprises make and size layersand abrasive particles as shown, for example, in FIG. 2. Referring nowto FIG. 2, exemplary coated abrasive article 200 comprises vulcanizedfiber backing 212 having first and second opposed major surfaces 231,232, respectively. Reinforcing material 211 is distributed substantiallythroughout vulcanized fiber backing 212. Optional backsize 213 isdisposed on second major surface 232, and optional presize 215 isaffixed to first major surface 231. Overlaying optional presize 215 andaffixed to backing 212 is abrasive layer 230 comprising: make layer 216in which are embedded abrasive grits 218, and size layer 217 whichoverlays and is affixed to make layer 216 and abrasive grits 218.Optional supersize 219 overlays size layer 217.

The basis weight of the make layer utilized may depend, for example, onthe intended use(s), type(s) of abrasive particles, and nature of thecoated abrasive article being prepared, but generally will be in therange of from 1, 2, or 5 to 20, 25, 400, or even 600 grams per squaremeter (i.e., gsm). The make layer is generally applied as a make layerprecursor that upon subsequent solidification (e.g., by curing orcooling) forms a layer of binder material of sufficient strength tosecure abrasive particles to the backing. The make layer precursor maybe applied by any known coating method for applying a make layerprecursor to a backing, including, for example, roll coating, extrusiondie coating, curtain coating, knife coating, gravure coating, and spraycoating. Examples of make layer precursors include curable materialscomprising phenolics, aminoplasts, poly(meth)acrylates, polyepoxides,polyisocyanates, hide glue, and combinations thereof.

After applying a make layer precursor to the reinforced vulcanized fiberbacking, and prior to solidification of the make layer precursor (e.g.,by curing), abrasive particles are deposited onto the make layer.

Exemplary useful abrasive particles include fused aluminum oxide basedmaterials such as aluminum oxide, ceramic aluminum oxide (which mayinclude one or more metal oxide modifiers and/or seeding or nucleatingagents), and heat-treated aluminum oxide, silicon carbide, co-fusedalumina-zirconia, diamond, ceria, titanium diboride, cubic boronnitride, boron carbide, garnet, flint, emery, sol-gel derived abrasiveparticles, and blends thereof. Examples of sol-gel abrasive particlesinclude those described U.S. Pat. No. 4,314,827 (Leitheiser et al.);U.S. Pat. No. 4,518,397 (Leitheiser et al.); U.S. Pat. No. 4,623,364(Cottringer et al.); U.S. Pat. No. 4,744,802 (Schwabel); U.S. Pat. No.4,770,671 (Monroe et al.); U.S. Pat. No. 4,881,951 (Wood et al.); U.S.Pat. No. 5,011,508 (Wald et al.); U.S. Pat. No. 5,090,968 (Pellow); U.S.Pat. No. 5,139,978 (Wood); U.S. Pat. No. 5,201,916 (Berg et al.); U.S.Pat. No. 5,227,104 (Bauer); U.S. Pat. No. 5,366,523 (Rowenhorst et al.);U.S. Pat. No. 5,429,647 (Larmie); U.S. Pat. No. 5,498,269 (Larmie); andU.S. Pat. No. 5,551,963 (Larmie); the disclosures of which areincorporated herein by reference. The abrasive particles may be in theform of, for example, individual particles, agglomerates, abrasivecomposite particles, and mixtures thereof.

Exemplary agglomerates are described, for example, in U.S. Pat. No.4,652,275 (Bloecher et al.) and U.S. Pat. No. 4,799,939 (Bloecher etal.), the disclosures of which are incorporated herein by reference. Itis also within the scope of the present invention to use diluenterodible agglomerate grains as described, for example, in U.S. Pat. No.5,078,753 (Broberg et al.), the disclosure of which is incorporatedherein by reference. Abrasive composite particles comprise abrasivegrains in a binder.

Exemplary abrasive composite particles are described, for example, inU.S. Pat. No. 5,549,962 (Holmes et al.), the disclosure of which isincorporated herein by reference.

Coating weights for the abrasive particles may depend, for example, onthe specific coated abrasive article desired, the process for applyingthe abrasive particles, and the size of the abrasive particles, buttypically range from 1 to 2000 grams per square centimeter (gsm).

The basis weight of the size layer will also necessarily vary dependingon the intended use(s), type(s) of abrasive particles, and nature of thecoated abrasive article being prepared, but generally will be in therange of from 1 or 5 gsm to 300, or even 800 gsm, or more.

The size layer is generally applied as a size layer precursor that uponsubsequent solidification (e.g., by curing or cooling) forms a layer ofbinder material of sufficient strength to secure the abrasive particlesto the make layer. The size layer precursor may be applied by any knowncoating method for applying a size layer precursor to a backing,including, for example, roll coating, extrusion die coating, curtaincoating, knife coating, gravure coating, and spray coating. Examples ofsize layer precursors include curable materials comprising at least oneof phenolic resins, aminoplasts, poly(meth)acrylates, polyepoxides,polyisocyanates, hide glue, urea-formaldehyde resins,melamine-formaldehyde resins, and combinations thereof.

Details concerning coated abrasive articles comprising abrasiveparticles and make and size layers, and optional supersize are wellknown and are described, for example, in U.S. Pat. No. 4,734,104(Broberg); U.S. Pat. No. 4,737,163 (Larkey); U.S. Pat. No. 5,203,884(Buchanan et al.); U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat.No. 5,378,251 (Culler et al.); U.S. Pat. No. 5,417,726 (Stout et al.);U.S. Pat. No. 5,436,063 (Follett et al.); U.S. Pat. No. 5,496,386(Broberg et al.); U.S. Pat. No. 5,609,706 (Benedict et al.); U.S. Pat.No. 5,520,711 (Helmin); U.S. Pat. No. 5,954,844 (Law et al.); U.S. Pat.No. 5,961,674 (Gagliardi et al.); U.S. Pat. No. 4,751,138 (Tumey etal.); U.S. Pat. No. 5,766,277 (DeVoe et al.); U.S. Pat. No. 6,077,601(DeVoe et al.); U.S. Pat. No. 6,228,133 (Thurber et al.); and U.S. Pat.No. 5,975,988 (Christianson); the disclosures of which are incorporatedherein by reference.

According to another embodiment of the present invention, the coatedabrasive article has an abrasive layer comprising a layer of abrasiveparticles dispersed in a binder as shown, for example, in FIG. 3.Referring now to FIG. 3, exemplary coated abrasive article 300 comprisesvulcanized fiber backing 312 having first and second opposed majorsurfaces 331, 332, respectively. Reinforcing material 311 is distributedsubstantially throughout backing 312. Optional backsize 313 is disposedon second major surface 332, and optional presize 315 is affixed tofirst major surface 331. Overlaying optional presize 315 and affixed tobacking 312 is abrasive layer 330, which comprises a plurality ofabrasive grits 318 distributed throughout binder 309.

In some embodiments of coated abrasive articles according to the presentinvention, the abrasive layer comprises a dispersion of abrasiveparticles in a binder (typically coated as a slurry of abrasiveparticles in a binder precursor. Slurry coating techniques are wellknown in the abrasive art, and include those described, for example, inU.S. Pat. No. 5,378,251 (Culler et al.); U.S. Pat. No. 5,942,015 (Culleret al.); and U.S. Pat. No. 6,277,160 (Stubbs et al.); the disclosures ofwhich are incorporated herein by reference. Examples of suitable binderprecursors include curable materials comprising phenolics, aminoplasts,poly(meth)acrylates, polyepoxides, polyisocyanates, and combinationsthereof. Abrasive particles used in this embodiment include all of thosepreviously listed hereinabove.

Coated abrasive articles according to the present invention can beconverted, for example, into belts, tapes, rolls, discs (includingperforated discs), and/or sheets. An exemplary coated abrasive discaccording to one embodiment of the present invention is shown in FIG. 4.

According to the present invention, it is found that problems of cuppingand/or curling due to moisture absorption are greatly reduced, generallyto a degree that they are no longer objectionable to users. This issurprising since the moisture uptake of the inventive coated abrasivesis typically virtually the same as for corresponding coated abrasives ofthe prior art.

Further, it is also surprisingly observed that coated abrasivesaccording to the present invention typically have improved cut ascompared to corresponding coated abrasives of the prior art.

For belt applications, two free ends of the abrasive sheet may be joinedtogether using known methods to form a spliced belt. A spliceless beltmay also be formed as described, for example, in U.S. Pat. No. 5,573,619(Benedict et al.), the disclosure of which is incorporated herein byreference.

Coated abrasive articles according to the present invention are usefulfor abrading a workpiece. One such method includes frictionallycontacting at least a portion of the abrasive layer of a coated abrasivearticle with at least a portion of a surface of the workpiece, andmoving at least one of the coated abrasive article or the workpiecerelative to the other to abrade at least a portion of the surface.

Examples of workpiece materials include metal, metal alloys, exoticmetal alloys, ceramics, glass, wood, wood-like materials, composites,painted surfaces, plastics, reinforced plastics, stone, and/orcombinations thereof. The workpiece may be flat or have a shape orcontour associated with it. Examples of specific workpieces includemetal components, plastic components, particleboard, camshafts,crankshafts, furniture, and turbine blades.

Coated abrasive articles according to the present invention may be usedby hand and/or used in combination with a machine. At least one or bothof the coated abrasive article and the workpiece is generally movedrelative to the other when abrading. Abrading may be conducted under wetor dry conditions. Exemplary liquids for wet abrading include water,water containing conventional rust inhibiting compounds, lubricant, oil,soap, and cutting fluid. The liquid may also contain defoamers,degreasers, and/or the like.

Objects and advantages of this invention are further illustrated by thefollowing non-limiting examples, but the particular materials andamounts thereof recited in these examples, as well as other conditionsand details, should not be construed to unduly limit this invention.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in theexamples and the rest of the specification are by weight, and allreagents used in the examples were obtained, or are available, fromgeneral chemical suppliers such as, for example, Sigma-Aldrich Company,Saint Louis, Mo., or may be synthesized by conventional methods.

The following abbreviations are used throughout the Examples thatfollow: VF vulcanized fiber web, 0.6 mm (33 mil) thick, obtained underthe trade designation “DYNOS FIBRE” from Troplast A.G., Troisdorf,Germany PAZ polyaziridine, obtained under the trade designation “XR2990”from H.B. Fuller Company, Vadnais Heights, Minnesota SS sodium silicate,37% aqueous solution “N” obtained from PQ Corporation, Valley Forge, PAX100 nonionic surfactant, “Triton X-100”, obtained from Hach Corp.,Ames, IA PR 75% aqueous solution of phenol-formaldehyde resin having aphenol to formaldehyde ratio of 1.5-2.1:1, catalyzed with 2.5 percentpotassium hydroxide PS propylene glycol monomethyl ether, obtained underthe trade designation “POLYSOLV MPM” from Arch Chemicals Inc.,Brandenburg, Kentucky AR thermosettable acrylic latex, obtained underthe trade designation “CARBOCURE TSR 72” from Noveon Inc., Cleveland,Ohio RNF moisture-resistant vulcanized fiber, both sides coated withpolyurethane, obtained under the trade designation “RNF-77” from ToyoFibre (USA) Inc., Schaumburg, Illinois NFK moisture-resistant vulcanizedfiber, believed to be impregnated with a dicyandiamide/formaldehyderesin, obtained under the trade designation “NFK- 88” from Toyo Fibre(USA) Inc. AP ceramic aluminum oxide abrasive particles, grade 36,obtained under the trade designation “CUBITRON” from 3M Company, SaintPaul, Minnesota. CACO calcium carbonate filler obtained under the tradedesignation “HUBERCARB Q325” from J. M. Huber Corporation, Fairmount,Georgia CRY filler, obtained under the trade designation “CRYOLITE TYPERTN-C” from Koppers Trading, Pittsburgh, PennsylvaniaTest MethodsCurl Test Method 1

Controlled humidity chambers were constructed using saturated saltsolutions as described in ASTM E104-02. A 23% relative humidity (RH)chamber was made using saturated potassium acetate, a 43% RH chamber wasmade using saturated potassium carbonate and an 85% RH chamber was madeusing saturated potassium chloride. The chambers consisted of a 5-gallonpail with a sealable lid containing a shallow reservoir of the saturatedsalt solution. Test disc samples were suspended in the chamber by meansof a horizontal wire, which was passed through the disc center hole andwas secured to the rim of the pail.

One side of each of the example treated fiber discs was completelycovered with aluminum foil tape (“Scotch Brand 425”, 3M Company), tosimulate the rigid restraining effect of an abrasive coating. The tapecoated discs were compressed between metal plates until flat andconditioned in the 43% RH chamber for a week. The initial curl of eachdisc was then measured. Four samples were used for each of the examplecompositions. Curl was measured by placing each fiber disc on a flatsurface, concave side down, and measuring the distance through thecenter hole from the flat surface to the uppermost surface of the fiberdisc. Curl was measured in millimeters.

Half of each example disc population (2 discs) was then put in eitherthe 23% RH or 85% RH chamber. After 2 weeks, the example fiber discswere removed and their degree of curl was again measured and the changein curl from the initial conditions was calculated. Curl index wascalculated for each fiber disc by adding the absolute values of thechanges in shape for both the 85% RH and 23% RH tests. The curl indexwas used as an indicator of shape stability.

Curl Test Method 2

Curl of abrasive discs was measured after equilibration for at least oneweek under ambient relative humidity conditions of 20% RH. The abrasivediscs were placed on a flat surface, concave side down, and thedisplacement between the surface and uppermost surface of the disc wasmeasured through the center hole expressed in millimeters. Curl awayfrom the abrasive face is positive and toward the abrasive face isnegative.

The discs were then placed in a thermostatically controlled oven,concave side up, for 3 hours at 60° C. to dry the fiber and initiatecurl. The discs were removed from the oven and curl was measured againas above. The change in curl was then calculated by subtracting theinitial curl from the final curl.

Grinding Performance Test

This test was designed to measure the effectiveness of an abrasive discconstruction for the removal of metal from a workpiece by measuring howthe cut rate changes with time and the total amount of metal usefullyremoved over the life of the abrasive disc. The coated abrasive disc wasmounted on a beveled aluminum back up pad and driven at a speed of 5,500rpm. A portion of the disc overlaying the beveled edge of the back uppad was contacted with the face of a 1.25 cm by 18 cm 1018 mild steelworkpiece at about 6 kg load. Each disc was used to grind a separateworkpiece for one-minute intervals for a total of 20 minutes or untilthe disc failed or the cut rate dropped below 20 grams per minute. Theamount of metal removed from each workpiece was recorded. The initialcut was reported as the amount of metal removed during the firstone-minute interval. The final cut was reported as the amount of metalremoved during the final one-minute interval. The total cut was thecumulative amount of metal removed from the workpieces over the entireuseful life of the abrasive disc or 20 one-minute intervals, whicheverwas reached first. The cut data is reported in grams of workpiece metalremoved.

General Procedure for Preparing Polyaziridine Impregnated VulcanizedFiber Discs

Crosslinked vulcanized fiber discs were prepared by saturation withaqueous solutions of known polyaziridine concentration. Six 17.8 cm (7in.) diameter discs cut from VF were submerged in aqueous solutions ofPAZ containing 0.1 percent by weight X100. After 2 hours, the saturatedfiber discs were removed from the liquid and excess superficial solutionwas wiped from the disc surface with a paper towel. The differencebetween the dry disc weight and the saturated disc weight was recordedand the weight percent aziridine incorporated in the disc was calculatedfrom this weight gain and the percent aziridine in the saturatingsolution. The discs were allowed to air dry overnight. The treated discswere then placed in between metal plates and compressed until flat. Thecompressed assembly was maintained for 24 hours at 85% relative humidity(RH) to allow the discs to assume a flat shape. The aziridine in thediscs was then thermally reacted by heating the compressed disc assemblyto 100° C. for 1 hour and 125° C. for 24 hours.

Impregnated Backings 1-4

Polyaziridine impregnated vulcanized fiber discs were prepared accordingto the Procedure for Preparing Polyaziridine Impregnated VulcanizedFiber Discs using the polyaziridine solutions of specificconcentrations, and resulting in incorporation levels as indicated inTable I (below). TABLE I CONCENTRATION OF INCORPORATION IMPREGNATED PAZ,LEVEL, BACKING percent by weight percent by weight 1 1 0.46 2 3 1.37 3 52.29 4 10 4.54Comparative Backing A

As a control for the effect of water saturation, fiber discs (17.8 cm (7in.) diameter with a 2.2 cm (⅞ inch) diameter center hole) weresaturated with a solution of 0.1 percent by weight X100 in deionizedwater. The discs were allowed to air dry and were dried in an oven for 1hour at 100 and 24 hours at 125° C. while compressed to a flat shape.

General Procedure for Preparing Phenolic Resin Impregnated VulcanizedFiber Discs

Method 1

In this method of saturation, phenolic resin was incorporated intovulcanized fiber in a vacuum chamber. A phenolic resin solution wasprepared using PR. Three hundred grams of this phenolic solution wasdiluted with 80 grams of deionized water. The diluted resin solution wasadded to a glass crystallization dish of sufficient diameter to containand submerge a 17.8 cm (7 in.) diameter VF disc. A single fiber disc wasadded to the container and the whole assembly was placed in a vacuumchamber equipped with a pump. The air was evacuated from the chamber fora period of 2 minutes, and then air was readmitted to restoreatmospheric pressure. This cycle was repeated three times. The fiberdisc was then removed from the phenolic solution and superficial resinwas removed by pressing between layers of paper toweling. The individualdiscs were restrained in a flat shape between metal plates and dried for2 hours at 90° C. followed by cure for 12 hours at 105° C.

Method 2

PR was diluted with water and placed in a shallow pan. Six weighed 17.8cm (7 in.) diameter VF discs were submerged in this solution for aperiod of 18 hours. Superficial solution was wiped from the surface ofthe discs with paper toweling and the discs were reweighed. The percentincorporation of phenolic resin in the fiber was calculated from theweight increase and the solution concentration. The discs were air driedand then cured as described in Method 1.

Method 3

PR was diluted a 1:1 (wt./wt.) blend of PS and water, and placed in ashallow pan. Six weighed 17.8 cm (7 in.) diameter VF discs weresubmerged in this solution for a period of 18 hours. Superficialsolution was wiped from the surface of the discs with paper toweling andthe discs were reweighed. The percent incorporation of phenolic resin inthe fiber was calculated from the weight increase and the solutionconcentration. The discs were air dried and then cured as described inMethod 1.

Impregnated Backings 5-8

Phenolic resin impregnated vulcanized fiber discs were preparedaccording to the Procedure for Preparing Phenolic Resin ImpregnatedVulcanized Fiber Discs using the phenolic resin solutions of specificconcentrations, and resulting in incorporation levels as indicated inTable II (below). TABLE II CONCENTRATION IN- OF PHENOLIC CORPORATIONIMPREGNATED RESIN, LEVEL, BACKING METHOD percent by weight percent byweight 5 1 59 not determined 6 3 15 3.30 7 3 37.5 6.60 8 2 60 15.65Impregnated Backing 9

Acrylic latex impregnated vulcanized fiber discs were prepared bysaturation with AR. Six 17.8 cm (7 in.) diameter discs cut from VF weresubmerged in AR. After 2 hours, the saturated fiber discs were removedfrom the liquid and excess superficial solution was wiped from the discsurface with a paper towel. The discs were allowed to air dry overnight.The treated discs were then placed in between metal plates andcompressed until flat. The compressed assembly was maintained for 24hours at 85 percent relative humidity to allow the discs to assume aflat shape. The latex in the discs was then thermally reacted by heatingthe compressed disc assembly to 100° C. for 1 hour.

Impregnated Backing 10

This was NFK as received from the manufacturer, cut into 17.8 cm (7 in.)diameter test discs having a 2.2 cm (⅞-inch) diameter center hole.

Comparative Backing B

This was VF as received from the manufacturer, cut into 17.8 cm (7 in.)diameter test discs having a 2.2 cm (⅞ inch) diameter center hole.

Example 11

This was RNF as received from the manufacturer, cut into 17.8 cm (7 in.)diameter test discs having a 2.2 cm (⅞-inch) diameter center hole.

Impregnated Backings 1-4 and 6-9 and Comparative Backings A and B weremeasured for shape stability using Curl Test Method 1. The results areshown in Table III below. TABLE III IMPREGNATED CURL INDEX, BACKING mm 111, 15 2 17, 13 3 16, 14 4 15, 17 6 1, 2 7 11, 9  8 7, 4 9 4, 8Comparative Backing A 29, 22Coated Abrasive Disc Preparation Method

A make resin was coated onto one surface of the fiber backing disc beingtested to a level of 170 grams/meter² (gsm) based on wet weight. Themake resin consisted of 48 percent by weight PR and 52 percent by weightCACO, which was diluted to 81 percent by weight solids with water.Immediately after coating the make resin, AP was electrostaticallycoated onto the make resin to an add on weight of 780 gsm. The coateddisc was then heated at 77° C. for 15 minutes and then at 93° C. for 90minutes to partially cure the make resin. A size resin was then coatedover the surface of the make resin and mineral grain to a target weightof 530 gsm wet weight. The size resin consisted of 32% PR and 68% CRY,diluted to 78% solids with water The size resin was cured at 77° C. for1 hour and then 102° C. for 16 hours. The resultant coated abrasivediscs were flexed twice in orthogonal directions over a 2.54-centimeter(1-inch) diameter rod before testing. For reference, coated abrasivedisc prepared from backings are designated as the correspondingExamples. Hence, Impregnated Backing I leads to Example 1 andComparative Backing B leads to Comparative Example B.

Example coated abrasive discs 5-11 and Comparative Example B wereevaluated for shape stability using Curl Test Method 2. Results arereported in Table IV (below). TABLE IV Change in Curl, Example mm 5 0,−1, 0, 1 6 3 7 1, 1 8 0, 0 9 4 10  2, 4 11  1 Comparative 10, 11 ExampleB

The grinding performance cut rate data for the coated abrasive discswere measured according to the Grinding Performance Test, the results ofwhich are reported in Table V (below). TABLE V EXAMPLE TOTAL CUT, gINITIAL CUT, g FINAL CUT, g 1  195.56* 97.5 90.06  953.3  101.9 35.13 3 76* 76 76 4  390.18* 102.1 81.46  156.24* 98.79 57.45 5 1493.3 103.8926.59 1419.43 99.1 23.31 6 1043.7 94.59 14.11 1119.2 90.03 21.32 7 972.1 101.3 12.3  937.99 92.76 10.27 8 1107.15 102.92 11.4 1007.86 98.87.57 9  274.78* 97.81 78.07  643.99* 102.36 105.74 10  1280.1* 103 79.61570.06 102.54 37.94 11   509.8* 97.4 107.1 1193.62 98.39 59.09Comparative 1070.62 94.61 17.78 Example B 1089.09 109.77 12.89 1126.76102.5 14.17 1109.0 91.7 19.3*Indicates that the test disc broke or was damaged during testing andthe test was stopped.

The grinding performance cut rate data for the coated abrasive discs ofExample 5 and Comparative Example B were measured according to theGrinding Performance Test, the results of which are reported in Table VI(below). TABLE VI INCREMENTAL CUT, g COMPARATIVE INTERVAL EXAMPLE 5EXAMPLE B 1 104 86 5 104 90 10 84 63 15 57 34 20 32 10

1. A coated abrasive article comprising a reinforced vulcanized fiberbacking having first and second major surfaces, the first major surfacehaving an abrasive layer affixed thereto, wherein the reinforcedvulcanized fiber backing has a reinforcing material distributedsubstantially throughout the vulcanized fiber backing, wherein thereinforcing material comprises from 0.1 to 20 percent by weight, basedon the combined weight of the reinforcing material and vulcanized fiberbacking, and wherein the reinforcing material comprises a reactionproduct of an aqueous organic curable material selected from the groupconsisting of phenolic resins, aldehydes, aminoplasts, urea-formaldehyderesins, polyaziridines, polyepoxides, polyisocyanates, curable latexemulsions, and combinations thereof.
 2. A coated abrasive articleaccording to claim 1, wherein the reinforcing material is distributedsubstantially uniformly throughout the vulcanized fiber backing.
 3. Acoated abrasive article according to claim 1, wherein the reinforcingmaterial comprises at least one material that is a reaction product ofat least one curable material selected from the group consisting ofphenolic resins, aminoplasts, urea-formaldehyde resins, curable latexemulsions, and combinations thereof.
 4. A coated abrasive articleaccording to claim 1, wherein the abrasive article comprises an abrasivedisc.
 5. A coated abrasive article according to claim 1, wherein theabrasive article comprises an endless abrasive belt.
 6. A coatedabrasive article according to claim 1, wherein the reinforcing materialcomprises from 5 to 15 percent by weight, based on the combined weightof the reinforcing material and vulcanized fiber backing.
 7. A coatedabrasive article according to claim 1, wherein the reinforced vulcanizedfiber backing has a thickness in a range of from 0.15 to 1.8millimeters.
 8. A coated abrasive article according to claim 1, whereinthe abrasive layer comprises make and size layers.
 9. A coated abrasivearticle according to claim 1, wherein the abrasive layer comprisesabrasive particles distributed in a binder.
 10. A coated abrasivearticle according to claim 1, wherein the abrasive layer comprises areaction product of components comprising at least one of a polyepoxide,a poly(meth)acrylate, urea-formaldehyde resin, melamine-formaldehyderesin, phenolic resin, or a combination thereof.
 11. A coated abrasivearticle according to claim 1, wherein the abrasive article furthercomprises at least one of a presize, subsize, backsize, tie layer orsupersize.
 12. A method of abrading a surface of a workpiece, the methodcomprising: providing a coated abrasive article according to claim 1;frictionally contacting the abrasive layer with a surface of theworkpiece; and moving at least one of the abrasive layer and the surfaceof the workpiece relative to the other to abrade at least a portion ofthe surface of the workpiece.
 13. A method of making a coated abrasivearticle, the method comprising: impregnating a vulcanized fiber backinghaving first and second major surfaces with a curable material; at leastpartially curing the curable material to provide a reinforcing materialwherein the reinforcing material comprises from 0.1 to 20 percent byweight, based on the combined weight of the reinforcing material andvulcanized fiber backing, and wherein the reinforcing material comprisesa reaction product of an aqueous organic curable material selected fromthe group consisting of phenolic resins, aldehydes, aminoplasts,urea-formaldhyde resins, polyaziridines, polyepoxides, polyisocyanates,curable latex emulsions, and combinations thereof; and affixing anabrasive layer to the first major surface of the reinforced vulcanizedfiber backing.
 14. A method of making a coated abrasive articleaccording to claim 13, wherein the curable material is selected from thegroup consisting of phenolic resins, aminoplasts, urea-formaldehyderesins, curable latex emulsions, and combinations thereof.
 15. A methodof making a coated abrasive article according to claim 13, wherein thereinforcing material comprises from 5 to 15 percent by weight, based onthe combined weight of the reinforcing material and vulcanized fiberbacking.
 16. A method of making a coated abrasive article according toclaim 13, wherein the resin impregnated vulcanized fiber backing has athickness in a range of from 0.15 to 1.8 millimeters.
 17. A method ofmaking a coated abrasive article according to claim 13, wherein theabrasive layer comprises make and size layers.
 18. A method of making acoated abrasive article according to claim 17, further comprisingapplying a supersize to the size layer.
 19. A method of making a coatedabrasive article according to claim 13, wherein the abrasive layercomprises a slurry layer.
 20. A method of making a coated abrasivearticle according to claim 13, wherein the abrasive article comprises anabrasive disc.
 21. A method of making a coated abrasive articleaccording to claim 13, wherein the abrasive article comprises an endlessabrasive belt.
 22. A method of making a coated abrasive articleaccording to claim 13, wherein at least one of the make or size layerscomprises a reaction product of components comprising at least one of apolyepoxide, a poly(meth)acrylate, urea-formaldehyde resin,melamine-formaldehyde resin, phenolic resin, or a combination thereof.